diff options
| author | Alexander Graf <graf@amazon.com> | 2023-12-07 23:56:54 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-12-15 17:23:00 +0100 |
| commit | 2678fd2fe9ee2c569e9cb6b17e786bc8f0753538 (patch) | |
| tree | 39376d0d83d700190d27c1f48b3103edf4b96807 /Documentation | |
| parent | 5133bee62f0ea5d4c316d503cc0040cac5637601 (diff) | |
initramfs: Expose retained initrd as sysfs file
When the kernel command line option "retain_initrd" is set, we do not
free the initrd memory. However, we also don't expose it to anyone for
consumption. That leaves us in a weird situation where the only user of
this feature is ppc64 and arm64 specific kexec tooling.
To make it more generally useful, this patch adds a kobject to the
firmware object that contains the initrd context when "retain_initrd"
is set. That way, we can access the initrd any time after boot from
user space and for example hand it into kexec as --initrd parameter
if we want to reboot the same initrd. Or inspect it directly locally.
With this patch applied, there is a new /sys/firmware/initrd file when
the kernel was booted with an initrd and "retain_initrd" command line
option is set.
Signed-off-by: Alexander Graf <graf@amazon.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20231207235654.16622-1-graf@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-firmware-initrd | 8 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 5 |
2 files changed, 11 insertions, 2 deletions
diff --git a/Documentation/ABI/testing/sysfs-firmware-initrd b/Documentation/ABI/testing/sysfs-firmware-initrd new file mode 100644 index 000000000000..20bf7cf77a19 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-firmware-initrd @@ -0,0 +1,8 @@ +What: /sys/firmware/initrd +Date: December 2023 +Contact: Alexander Graf <graf@amazon.com> +Description: + When the kernel was booted with an initrd and the + "retain_initrd" option is set on the kernel command + line, /sys/firmware/initrd contains the contents of the + initrd that the kernel was booted with. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 65731b060e3f..51575cd31741 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2438,7 +2438,7 @@ between unregistering the boot console and initializing the real console. - keepinitrd [HW,ARM] + keepinitrd [HW,ARM] See retain_initrd. kernelcore= [KNL,X86,IA-64,PPC] Format: nn[KMGTPE] | nn% | "mirror" @@ -5580,7 +5580,8 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). - retain_initrd [RAM] Keep initrd memory after extraction + retain_initrd [RAM] Keep initrd memory after extraction. After boot, it will + be accessible via /sys/firmware/initrd. retbleed= [X86] Control mitigation of RETBleed (Arbitrary Speculative Code Execution with Return Instructions) |